Hi. I have a 20,000 gallon in ground pool with a cartridge filter that always had good chlorine (and other) readings for years with tabs in a floater. My pump (3/4 hp variable speed that always ran on the low speed) went out and I got a new 1 hp pump (single speed). Ever since then (and I mean almost immediately) I cannot keep chlorine in the pool. Nothing changed but the pump. I run it the same number of hours per day (6-8) as I did before. There is no free or total chlorine being maintained. I now put a gallon of 8% bleach in every day and after 24 hours it shows nothing. Initially I was using the floater with tabs and nothing. I added another floater with tabs and nothing. I use phosfree and the phosphorus reading is very low so that is not it. I asked a guy at the pool store if too large a pump could cause this and he said yes. I asked another and he said no. The circulation is clearly much greater than it used to be. I am at a loss. Any thoughts? Thanks!